COLUMBATLS. 


THLSIS 


PRESENTED  TO  THE.  FACULTY  OF  THE.  DEPARTMENT  OF 
PHILOSOPHY  OF  THE.  UNIVERSITY  OF  PENNSYLVANIA 
IN  PARTIAL  FULFILMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  DOCTOR 
OF  PHILOSOPHY 


BY 


MATTHEW  HUME  BEDFORD,  A.B., 


CENTRAL  UNIVERSITY, 
KENTUCKY. 


ESCHENBACH  PRINTING  COMPANY 
EASTON,  PA. 

1905 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 

University  of  Illinois  Urbana-Champaign  Alternates 


https://archive.org/details/columbatesOObedf 


tr  it.  w'. 


COLUMBATLS 


INTRODUCTION. 

This  thesis  represents  but  one  chapter  in  a  series  of  investiga¬ 
tions  of  columbium  and  tantalum  which  have  been  carried  out  in 
the  past  and  are  still  being  continued  in  this  laboratory.  It 
presents  the  results  obtained  in  the  preparation  of  sodium  col- 
umbate  by  several  methods  and  several  other  columbates  derived 
therefrom. 

historical. 


In  making  a  review  of  the  literature  on  the  columbates,  it  was 
noticed  that  each  method  of  preparation  gave  salts  to  which 
different  formulas  were  assigned. 

H.  Rose1  prepared  a  sodium  columbate  by  the  fusion  of  columbic 
oxide  with  sodium  hydroxide  in  a  silver  crucible.  He  assigned  to 
this  salt  the  formula  Na20.Cb205.5H20  and  also  obtained  one  with 
7H20.  After  Marignac  had  shown  that  Rose’s  “Unterniob- 
saure,”  Cb203,  was  really  Cb205,  Rammelsberg2  recalculated 
Rose’s  results  and  gave  these  salts  the  formula  Na2O.Cb205.6H20 
and  9H20.  Rose  said,  “of  all  the  salts  of  tantalic  and  columbic 
acids,  this  sodium  salt  is  obtained  in  the  best  crystalline  form, 
Xand  it  is  also  the  most  stable.” 

He  also  states  that  in  the  preparation  of  the  neutral  salt  he 
obtained  a  basic  salt,  to  which  was  assigned  the  composition 
3Na20.2Cb205.24H203. 

He  gave  the  following  as  the  sodium  columbates  that  he  found 
well  defined : 

(1)  3Na20.Cb205,  obtained  by  long  fusion  of  the  oxide  with 
sodium  carbonate. 

(2)  3Na20.2Cb205.24H20. 

(3)  Na20.Cb205.6H20  and  9H20,  the  neutral  salt. 

(4)  4Na20.5Cb205,  the  only  acid  salt  of  ex:.Cc  ratio,  the  other 


1  Pogg.  Ann.,  11 3,  105. 

2  Jour,  fur  Chem.,  108,  77  (1869). 

3  Rammelsberg  :  Jour,  fur  Chem.,  108,  77  (1869). 


„ 15746 


4 


acid  salts  being  mixtures  (formulas  from  Rammelsberg’s  recalcula- 

Hermann1  prepared  a  sodium  columbate  to  which  he  assigned 
the  composition  5Nap.4Cb20,2iH20.  This  salt  was  made  by 
adding  sodium  hydroxide  to  a  solution  of  potassium  columbium 
oxyfluoride.  In  his  paper  he  called  attention  to  the  great  differ¬ 
ence  between  the  found  and  calculated  percentages  in  H.  Rose  s 

Marignac3  obtained  a  crystalline  potassium  columbate,  to 
which  he  assigned  the  formula,  4K2O.3CbA.4Hp  + 1 zAq,  but 
Rose  and  Hermann  were  unable  to  obtain  a  crystalline  salt.  T  is 
was  obtained  by  fusing  columbic  oxide  with  potassium  carbonate. 

On  recrystallization  this  salt  approached  the  composition 
8K20.7Cb205.9H20  +  32Aq.  It  had  a  tendency  to  form  super- 
saturated  solutions. 

He  also  described  three  other  salts  of  the  following  composition: 

3K20.2Cb205.6H20  +  7Aq. 

3K20.Na20.3Cb205.9H20. 

K20 . 3Cb  A-  5H20 . 

He  said  “Columbic  acid  with  sodium  formed  only  powdery 
crystalline’ salts,  which  suffered  decomposition  on  washing  with 

W  Santessen3  described  a  salt  to  which  he  assigned  the  composition 


K,0  2Cb20s.5iH20.  It  was  prepared  by  fusing  columbic  oxide 


with  the  calculated  amount  of  potassium  carbonate,  and  was  in¬ 
soluble  in  water.  When  a  large  excess  of  potassium  carbonate 
™  L,  h.  obtained  the  «K  **>■<%>,"**>  “  * 
after  extracting  the  melt  with  water.  The  salt  HaP^bAd  2 
was  found  to  be  soluble  in  water  while  the  salt  2Nap.3CbA.9Hp, 
obtained  by  fusing  the  above  salt  with  sodium  hydroxide,  was 

“  tw  described  four  series  of  salts  of  the  general  composition 
RO  Cb  O  2R0.Cb205,  3R0.Cb205  and  4R0.Cb205.  These  salts 
were  prepared  by  heating  Cb205  with  a  metallic  chloride  at  a  tem¬ 
perature  somewhat  below  that  at  which  the  chloride  volatilized 

■  Jour,  fur  Chem.,  Ill,  373  (1871)- 

2  Ibid.,  97*  449  (1866). 

3  Bull.  Soc.  Chim.,  (2)  24,  52. 

^  C.  R.,  81 »  266,  1266. 


5 


Larsson,1  in  order  to  obtain  columbates  of  a  constant  com¬ 
position,  tried  to  crystallize  the  precipitated  amorphous  colum¬ 
bates  by  fusing  them  with  the  chloride  of  the  corresponding  metal 
or  by  crystallizing  them  from  fused  boron  trioxide. 

He  obtained  the  following  salts.  Those  under  I  were  obtained 
by  heating  the  amorphous  columbates  with  the  metallic  chlorides, 
and  those  under  II  by  heating  them  with  boron  trioxide.  The 
amorphous  precipitates  used  in  the  fusions  were  obtained  from 
potassium  columbate,  but  he  did  not  assign  a  formula  to  the  latter. 


I 

4Mg0.Cb205 

2Ca0.Cb205 

Y203.Cb205 


II 

Mg0.Cb205 

Ca0.Cb205 

Y203.3Cb205 


CuO.Cb2Os 

Zn0.Cb205 

Cd0.Cb205 

3Mn0.5Cb205 

5Th02.i6Cb205 

Zr02.5Cb205 

A  number  of  other  metals  were  tried  but  their  ratios  were  as 
irregular  as  the  last  three  salts  under  II. 

Melikoff  and  Pissarjewsky2  describe  the  preparation  of  per- 
columbic  acid,  HCb04  +  nH20  and  potassium  percolumbate, 
K4Cb2On  +  3H20. 


SOURCE  OF  CORUMBIUM. 


The  columbic  oxide  used  in  this  investigation  had  been  carefully 
purified  by  Dr.  R.  D.  Hall.  It  was  prepared  from  the  columbite 
of  South  Dakota.  The  oxide  was  free  from  tin,  tungsten,  and 
tantalum,  but  it  contained  a  trace  of  titanium. 


EXPERIMENTAL  PART. 


Preparation  of  the  sodium  salt  by  Hermann’s  method.  Fifty 
grams  of  potassium  columbium  oxyfluoride  were  dissolved  in 
i  litre  of  hot  water  to  which  was  added  a  concentrated  solution  of 
150  grams  of  sodium  hydroxide.  A  white  powdery  precipitate 
was  formed,  and,  after  cooling,  the  supernatant  liquid  should  be 

1  Zeit.  fiir  anorg.  Chem.,  12,  188. 

2  Ibid.,  20,  340. 


6 


free  from  columbium.  If  this  was  not  the  case,  more  sodium 
hydrate  was  added.  The  precipitate  was  filtered  out  and  washed 
with  cold  water  until  the  filtrate  became  milky.  This  showed  that 
the  excess  of  sodium  hydroxide  had  been  washed  out.  It  was 
then  dried  as  far  as  possible  by  suction,  and  was  recrystallized 
three  times  from  distilled  water.  After  the  third  crystallization  it 
was  allowed  to  dry  in  the  air. 

This  salt  dissolved  in  water  without  leaving  any  residue  and 
was  very  stable.  Beautiful  crystals  could  be  obtained  when  the 
solution  was  allowed  to  cool  slowly.  It  was  found  that  it  was  best 
to  cool  rapidly  and  stir  well  as  it  formed  supersaturated  solutions 
very  readily. 

method  of  analysis. 

At  first  it  was  thought  that  it  would  be  necessary  to  get  the 
water  by  ignition  with  tungstic  oxide  because  Rose  said  that  when 
sodium  columbate  was  ignited,  sodium  hyroxide  and  columbic 
oxide  remained.  But  it  was  found  that  the  loss  on  ignition  of  the 
salt  alone  was  the  same  as  the  loss  on  ignition  of  the  mixture  of  the 
salt  and  tungstic  oxide.  The  ignited  sample  was  fused  with  4-5 
parts  of  potassium  bisulphate  and,  after  cooling,  the  melt  was 
boiled  up  with  water  until  completely  disintegrated.  The  col¬ 
umbic  oxide  was  filtered  out  and  thoroughly  washed,  ignited,  and 
weighed.  The  sodium  was  obtained  by  dissolving  a  sample  of  the  i 
salt  in  100  cc.  of  water  and  adding  5-10  drops  of  dilute  sulphuric 
acid.  After  boiling  a  few  minutes  the  precipitated  columbium 
hydrate  was  filtered,  washed  with  boiling  water,  the  precipitate 
ignited,  and  weighed  as  columbic  oxide.  The  filtrate  was  evaporated 
and  the  sodium  weighed  as  sulphate  after  ignition.  A  trace  of 
columbic  oxide  sometimes  remained  with  the  sodium  sulphate 
which  was  removed  by  taking  the  sulphate  up  with  water  and 
filtering.  After  evaporation  the  sodium  sulphate  was  again 
weighed. 

A.  0.3352  gram  sample  gave  0.0736  gram  loss  on  ignition  equal  to 

21.96  per  cent.  H20,  and  0.2063  gram  Cb2Os  equal  to  61.54 
per  cent. 

B.  0.2636  gram  gave  0.0582  gram  loss  on  ignition  equal  to  22.08 

per  cent.  H20,  and  0.1625  gram  Cb205  equal  to  61.65  per  cent. 


7 


C.  0.5058  gram  gave  0.1922  gram  Na2S04  equal  to  0.0839  gram 

Na20  equal  to  16.59  Per  cent. 

D.  0.5254  gram  gave  0.1993  gram  Na2S04  equal  to  0.0870  gram 

Na20  equal  to  16.57  Per  cent. 


Calculated  Percentage  found, 

percentage.  / - * - ■ 

7Na20 .  434  16.58  16.59  16.57 

6Cb206 .  1608  61.42  61.54  61.64 

32H20 .  576  22.00  21.96  22.08 


2618  100.00  100.09  100.29 

H.  Rose1  assigned  to  his  salt  the  formula  Na20.Cb205.6H20  and 
this  seems  to  have  been  the  one  generally  accepted. 

It  was  therefore  thought  at  first  that  the  salt,  obtained  by  the 
method  of  Hermann  as  above,  contained  an  extra  Na20  which 
would  be  eliminated  by  precipitating  an  aqueous  solution  of  the 
salt  by  alcohol.  This  was  done  and  the  following  analyses  of  an 
air-dried  sample  show  that  the  composition  of  the  salt  had  not 
altered,  except  in  its  water  content.  The  same  method  of  analysis 
was  used  as  in  the  case  of  the  preceding  salt. 

A.  0.2252  gram  sample  gave  0.1394  gram  of  Cb206  equal  to  61.90 

per  cent.,  and  0.0861  gram  Na2S04  equal  to  0.0379  gram 
Na20  equal  to  16.43  per  cent. 

0.2062  gram  sample  lost  0.0448  gram  on  ignition  equal  to 
21.73  Per  cent.  H20. 

B.  0.2236  gram  sample  gave  0.1392  gram  Cb2Os  equal  to  62.24 

per  cent.,  and  0.0847  gram  Na2S04  equal  to  0.0372  gram 
Na20  equal  to  16.62  per  cent.  0.3499  gram  sample  lost  on 
ignition  0.0761  gram  equal  to  21.46  H20. 


Calculated  Percentage  found. 

Percentage.  . - * - , 

7NazO .  434  16.69  16.43  16.62 

6Cb206 .  1608  61.85  61.90  62.24 

3iH20 .  558  21.46  21.73  21.46 


2600  100.00  100.06  100.32 

BARIUM  COLUMBATE,  7Ba0.6Cb205. i8H20. 

The  sodium  salt  prepared  by  Hermann’s  method  was  dissolved 
in  hot  water  and  a  dilute  solution  of  barium  chloride  was  added. 
1  “Rammelsberg’s  Recalculation,”  Jour,  fur  Chem.,  108,  77  (1869). 


8 


A  heavy  white  precipitate  was  formed  which  settled  very  quickly. 
This  precipitate  was  washed  by  decantation  with  boiling  water 
until  free  from  chlorides.  It  was  then  collected  on  a  filter  and 
dried  on  a  water-bath  for  one  and  a  half  hours.  It  was  ground 
for  analysis.  The  color  remained  white. 

method  of  analysis. 

The  sample  was  ignited  in  a  platinum  crucible  and  the  loss  was 
water.  This  ignited  residue  was  fused  with  a  flux  consisting  of 
equal  parts  of  sodium  and  potassium  carbonates  and  after  allow¬ 
ing  the  melt  to  cool,  it  was  taken  up  in  a  dilute  solution  of  oxalic 
acid.  After  acidifying  with  hydrochloric  acid  everything  went 
into  solution  on  warming.  When  all  of  the  barium  oxalate  had 
dissolved,  the  solution  was  brought  to  boiling  and  the  barium 
precipitated  as  sulphate  with  sulphuric  acid.  The  barium  sul¬ 
phate  was  filtered  out  and  treated  as  usual.  The  columbium 
was  obtained  in  the  filtrate  from  the  barium  sulphate  by  pre¬ 
cipitation  with  ammonium  hydroxide.  At  times  this  precipitate 
was  very  difficult  to  filter. 

A.  0.2222  gram  sample  lost  0.0240  gram  on  ignition  equal  to 

10.80  per  cent.,  H20,  and  gave  0.12 13  gram  BaS04  equal  to 
0.0796  gram  BaO  equal  to  35.83  per  cent.,  and  Cb205  in  this 
by  difference  53.37  per  cent. 

B.  0.5281  gram  sample  gave  0.2902  gram  BaS04  equal  to  0.1905 

gram  BaO  equal  to  36.08  per  cent.,  and  gave  0.2801  gram 
Cb205  equal  to  53.06  per  cent. 

0.5208  gram  sample  lost  0.0560  gram  on  ignition  equal  to  10.75 
per  cent.,  H20. 

This  gives  the  following: 


Calculated  Percentage  found, 
percentage.  , - * - *  Mean. 

7®aO .  1071  35.66  35.83  36.08  35.96 

6Cb206 .  1608  53.55  53.37  53.06  53.22 

i8H20 .  324  10.79  10.80  10.75  10.78 


3003  100.00  100.00  9989  9996 

SILVER  COLUMBATE,  7Ag20.6Cb205.5H20 
This  salt  was  obtained  by  adding  a  solution  of  silver  nitrate  to  a 
solution  of  the  sodium  columbate.  It  separated  as  a  white  pre¬ 
cipitate.  It  was  washed  with  boiling  water  by  decantation  until 


i 


9 


free  from  silver  and  then  collected  on  a  filter.  It  was  dried  on  a 
water-bath  for  an  hour.  It  was  ground  to  a  powder  for  analysis. 
It  had  a  slight  yellow  color. 

method  of  analysis. 

It  was  thought  at  first  that  the  loss  on  ignition  would  be  the 
water  and  the  oxygen  of  the  silver  oxide.  But  it  was  found  that 
the  loss  on  ignition  was  not  equivalent  to  the  oxygen  from  the 
silver  oxide.  Nitric  acid  would  not  dissolve  all  of  the  silver  from 
the  ignited  residue,  so  a  sample  was  ignited  in  a  current  of  dry  air 
and  the  water  was  collected  in  a  calcium  chloride  tube  and  weighed 
For  the  determination  of  the  silver  and  columbium  a  sample  was 
fused  with  potassium  bisulphate.  The  melt  was  taken  up  with 
oiling  water  and  the  columbium  determined  as  usual.  The  silver 
in  the  filtrate  from  the  columbium  hydrate  was  titrated  with 
standard  potassium  sulphocyanide. 

4.  0.3002  gram  sample  gave  0.1470  gram  Cb2Os  equal  to  4807 
per  cent.  4  w 

B.  0.3051  gram  sample  gave  0.1487  gram  Cb206  equal  to  48  75 
per  cent.  ^  '/0 

'•  0,2682  gram  SfmP,e  Save  °  I3I2  gram  Cb206  equal  to  4893 
per  cent,  and  o.  1306  gram  of  Ag20  equal  to  48.70  per  cent 

1  0  2818  gram  samPle  gave  0.0071  gram  of  water  equal  to  2  52 
per  cent.,  and  o.  1382  gram  Cb205  equal  to  49.05  per  cent.,  and 
0.1374  gram  Ag20  equal  to  48.74  per  cent. 

Calculated  Percentage  found. 

7  Ag-  O  ^  percentage.  Mean. 

. 2t  V9 

5h2o.5. . 16,8  4 ,4° 

y  2-7i  2.52 

v>  lit  .  ZZ22  100.00  100.17 

ammelsberg  ascribed  to  H.  Rose’s  silver  columbate  the  follow- 
ig  composition: 

Calculated  Percentage  found 

. 376  cbA . pe?;r  (H;Eose,) 

12O .  I92  4558  47-31 

Acl . .  •  18  _  __ 

_  r-77  1.98 

1  T  »..  1018  100.00  no 

Jour,  fur  Chem.,  108,  77  (1869).  99  74 


IO 


It  is  described  as  having  a  slight  yellow  color  on  precipitation 
and  as  turning  black  on  drying  at  100°. 

zinc  columbate,  7Zn0.6Cb205.25H20. 

This  salt  was  prepared  by  adding  a  solution  of  zinc  sulphate  to  a 
solution  of  the  sodium  columbate.  A  white  precipitate separa Jed 
Tattled  auicklv  It  was  washed  by  decantation  with  boiling 
“ £»  sulphate  and  «  »»  «*•  «  “  ‘ 
This  precipitate  wa,  dried  on  a  water-bath  and  ground  to  a 
A  fnr  nrifllvsis  It  remained  white  after  drying. 

Tt  might  be  mentioned  here  that  the  water  content  may  not  al¬ 
ways  remain  the  same  when  the  salt  is  dried  as  indicated  above 

method  of  analysis. 

The  sample  was  ignited  in  a  platinum  crucible,  the  loss  repre 

senting  the  water.  This  ignited  sample  was  fused  with  potassiun 
sen  ting  _  determined  as  usual.  Th< 


renting  the  water.  This  ignnea  bcunpi^  * 

bisulphate  and  the  columbic  oxide  determined  as  usua  . 

zinc  was  obtained  by  difference. 

A.  0.3018  gram  sample  lost  0.0520  gram  on  ignition  equal 
17.21  per  cent.  H20. 

*•  <0  poo 


^018  gram  sample  iubt  & -  - 

per  cent.  H20  and  gave  0.1842  gram  Cb206  equal  to  61.0 

Per  cent-  .  rb  _ _ or  cent 


-7t,0  . 

Calculated 

percentage. 

21.69 

APh  O  .  .  .  . 

.  1608 

61 . 18 

2cHoO . 

17-13 

2628 

100.00 

Percentage  found. 
Mean. 

21.86 

60.87 

17-27 


99-99 


In  order  to  show  that  any  other  formula,  that  wouldapproa 

this  composition,  will  not  give  the  “rreCt«“  given.' 
culated  percentages  for  the  1  : 1  and  8  .  7  ratios  are  g 

Percentage. 


Percentage. 

ZnO .  *9 -3* 

Cb2Ot .  63-59 

4H20 .  *7°9 


Percentage. 

_ _  21.23 

7Cb2Os .  61  16 

30II/.) .  17.61 


8ZnO 


100.00 


100.00 


Since  the  salts  which  have  been  described  show  conclusively 
that  they  were  not  of  the  RO.Cb205  and  probably  not  of  the 
8R0.7Cb20  type,  it  was  thought  that  sodium  columbate  should 
be  prepared  by  the  method  of  Rose. 

PREPARATION  OF  THE  SAET  BY  ROSE’S  METHOD. 

Ten  grams  of  the  ignited  columbic  oxide  were  fused  with  40 
grams  of  sodium  hydroxide  in  a  silver  crucible.  The  excess  of 
sodium  hydroxide  was  washed  out  and  the  sodium  columbate  was 
filtered  by  suction.  It  was  then  twice  recrystallized  from  water 
and  dried  in  the  air. 

Very  beautiful  crystals  of  this  salt  were  obtained  and  they  were 
completely  soluble  in  water.  They  were  slightly  dark  in  color, 
due  to  a  small  quantity  of  silver  oxide  which  could  not  be  removed 
by  filtration  from  their  solution. 

method  of  analysis. 

The  same  method  of  analysis  was  employed  as  that  described 
for  the  sodium  salt  prepared  by  Hermann’s  method. 

A.  0.3540  gram  sample  lost  0.0777  gram  on  ignition  equal  to  21.95 

per  cent.  H20,  and  gave  0.2175  gram  Cb2Os  equal  to  61.45 
per  cent. 

B.  0.3362  gram  sample  lost  0.0740  gram  on  ignition  equal  to  22.01 

per  cent.,  H20  and  gave  0.2066  gram  Cb206  equal  to  61.46 
per  cent. 

C.  0.4698  sample  gave  0.2883  gram  Cb205  equal  to  61.38  per  cent., 

and  gave  0.1792  gram  Na2S04  equal  to  0.0783  gram  Na20 
equal  to  16.65  Per  cent. 


7Na20. 

5Cb206 

i32H20. 


Percentage 

calculated. 

- - Percentage  found. - , 

A.  B.  C. 

434 

1608 

576 

16.58 

61.42 

22.00 

61.45  61.46  61.38 

21.95  22.01  . 

2618 

100.00 

Mean. 

16.65 

61.43 

21.98 


IOO.06 


H.  Rose1  gave  the  following  data  for  the  salt  prepared  in  this 
nanner. 


1  Recalculated  by  Rammelsberg,  Jour,  fur  Chem.,  108,  77  (1869). 


12 


Theory. 

Found. 

Na20 . 

.  62 

14. 16 

15-68 

Cb205 . 

.  268 

61 . 20 

60.82 

6H20 . 

.  108 

24.64 

438 

100.00 

The  sodium  salt  was  also  prepared  by  fusing  8  grams  of  columbic 
oxide  with  25  grams  of  sodium  carbonate  in  a  platinum  crucible. 
The  melt  was  taken  up  in  water  and  the  excess  of  sodium  car¬ 
bonate  washed  out  and  the  sodium  columbate  filtered  by  suction. 
This  was  recrystallized  from  water.  There  was  such  a  small  quan¬ 
tity  of  the  salt  that  it  could  not  be  crystallized  well  because  of  its 
tendency  to  form  a  supersaturated  solution.  However,  on  adding 
a  small  quantity  of  a  solution  of  sodium  carbonate,  it  came  out 
slowly  as  a  fine  powder.  This  was  washed  with  a  little  cold  water, 
and  allowed  to  dry  in  the  air.  This  salt  was  completely  soluble  in 
water. 

method  of  analysis. 

The  method  of  analysis  used  for  this  salt  was  the  same  as  that 
described  for  the  sodium  salt  prepared  by  the  other  two  methods. 


Percentage  Percentage  found, 

calculated.  Mean. 

7Na20‘ .  434  16.13  15.84 

6Cb2Os .  1608  59-78  60.20 

36H20 .  648  24.09  24.16 


2690  100.00  100.20 

CONCLUSIONS. 

Sodium  columbate  was  prepared  by  three  different  methods. 
The  results  obtained  showed  that  in  each  case  the  salts  had  the 
same  proportion  of  sodium  oxide  to  columbic  oxide.  The  one  pre¬ 
pared  by  fusing  columbic  oxide  with  sodium  carbonate  gave  a  salt 
with  four  molecules  of  water  more  than  the  other  two.  But  this 
may  be  explained  by  its  being  precipitated  with  sodium  carbonate. 
Sodium  oxide  could  not  be  dissolved  out  with  alcohol  to  form  a  salt 
of  the  ratio  Na2O.Cb206.  The  7  : 6  ratio  held  throughout  the 
barium,  silver,  and  zinc  salts.  The  barium  and  zinc  salts  did  not 
give  the  percentages  required  by  an  8  :  7  ratio,  although  the  re- 


i 


i3 


quirements  of  the  two  ratios  were  fairly  well  fulfilled  by  the  results 
obtained  for  most  of  the  other  salts. 

Rammelsberg  allowed  too  large  an  error  in  recalculating  Rose’s 
work,  allowing  as  much  as  3.1  per  cent,  for  columbic  oxide,  and 
3.41  per  cent,  for  mercury  in  his  mercurous  columbate.  Some 
of  Rose’s  results  come  very  close  for  a  7  :  6  ratio. 

SEPARATION  OF  COLUMBIC  AND  TUNGSTIC  ACIDS. 

This  study  arose  from  the  great  difficulty  that  was  experienced 
in  trying  to  separate  columbic  and  tungstic  oxides  in  a  salt  ob¬ 
tained  by  dissolving  moist  tungstic  oxide  in  a  boiling  solution  of 
sodium  columbate.  The  thought,  at  that  time,  was  to  put  col¬ 
umbic  oxide  in  with  tungstic  oxide  to  form  a  columbo-tungstate 
analogous  to  the  phospho- tungstates  and  vanado- tungstates.  A 
salt  was  obtained  that  crystallized  in  the  same  form  as  the  sodium 
columbate  and  contained  about  22.50  per  cent,  of  tungstic  oxide 
and  43.3  per  cent,  of  columbic  oxide.  This  salt  could  be  recrystal¬ 
lized  without  undergoing  any  decomposition,  as  the  following  will 
show: 

I.  Sample  from  first  crystallization  gave  15.64  Na20  and  84.35 
Cb205  + W03. 

II.  Sample  from  second  crystallization  gave  15.74  Na20  and  84.24 
Cb205  + W03. 

The  weight  of  the  water  was  subtracted  from  the  weight  of  the 
sample  before  the  calculations  were  made,  but  on  trying  to  pre¬ 
pare  this  salt  again  it  was  found  that  a  salt  of  a  slightly  different 
composition  was  obtained.  It  seems  that  with  further  study  a 
columbo-tungstate  can  be  made. 

In  the  separation  of  the  columbic  and  tungstic  acids  in  this  salt 
concordant  results  were  not  obtained  by  the  usual  method.  The 
first  method  tried  was  the  fusion  of  the  sample  with  a  mixture  of 
sodium  carbonate  and  sulphur.  It  will  be  sufficient  to  state  here 
that  the  results  varied  within  wide  limits,  even  on  mixtures  of 
weighed  quantities  of  columbic  and  tungstic  oxides.  Digestion 
of  the  ignited  sample  with  a  strong  solution  of  sodium  hydroxide 
was  next  tried,  but  did  not  give  satisfactory  results. 

A  short  review  of  the  methods  that  have  been  used  to  get 
columbium  and  tantalum  free  from  tin  and  tungsten  will  be  given 
here. 


Berzelius1  digested  the  oxides  with  yellow  ammonium  sulphide 
to  remove  the  tin  and  tungsten. 

Wohler2  said  that  it  was  sufficient  to  wash  the  oxides  with 
ammonium  sulphide  on  the  filter.  He  also  stated  that  it  would  be 
safer  to  fuse  the  oxides  with  three  times  their  weight  of  an  alkaline 
carbonate  and  sulphur,  and  then  wash  with  ammonium  sulphide. 

H.  Rose3  fused  the  oxides  with  sodium  carbonate  and  sulphur 
and  washed  with  ammonium  sulphide. 

Blomstrand4  used  the  method  of  Berzelius  instead  of  Rose’s. 
He  said  that  fusion  with  sodium  carbonate  and  sulphur  did  not 
give  good  results.  If  heated  too  high  some  columbate  was  formed 
and  would  go  into  solution  along  with  the  sulpho-tungstate  and 
sulpho-stannate.  And  if  it  was  not  heated  high  enough  the  action 
would  not  be  complete. 

Hall5  found  that  digesting  even  four  or  five  times  with  am¬ 
monium  sulphide  did  not  remove  all  of  the  tin  and  tungsten.  He 
then  had  recourse  to  Rose’s  method.  After  a  second  fusion  with 
sodium  carbonate  and  sulphur  he  could  not  get  a  test  for  tin  or 
tungsten.  This  proved  the  best  course  to  pursue  in  separating 
columbium  from  tungsten  and  tin. 

But  for  a  quantitive  separation  it  does  not  give  concordant  re¬ 
sults.  The  reasons  advanced  by  Blomstrand  seem  to  give  the  best 
explanation. 

Therefore,  another  method  for  the  quantitative  separation  of 
columbium  and  tungsten  was  sought.  One  of  the  thoughts  that 
suggested  itself  was  precipitation  of  the  columbic  oxide  with  a 
magnesia  mixture  in  an  alkaline  solution.  This  is  the  usual 
method  of  separating  phosphoric  and  tungstic  acids.  It  was  soon 
found  that  the  magnesium  columbate  could  not  be  weighed  as 
such. 

The  method  was  tried  on  weighed  quantities  of  columbic  and 
tungstic  oxides. 

1  Pogg.  Ann.,  4,  6. 

2  “Mineral  Analyse,”  p.  140. 

3  Handbuch  der  Anal.  Cliem.,  2,  336. 

4  Jour,  fur  Chem.,  99,  40. 

5  Jour.  Am.  Chem.  Soc.,  26,  1235. 


15 


procedure. 

Weighed  quantities  of  the  two  oxides  were  fused  with  potassium 
carbonate  (because  the  potassium  salts  are  more  soluble  than 
the  sodium).  The  melt  was  taken  up  in  150  cc.  of  water.  To  the 
potassium  carbonate  solution  an  excess  of  a  magnesia  mixture  was 
added.  The  precipitate  formed  was  allowed  to  stand  several 
hours  and  then  filtered.  It  was  washed  on  the  filter  five  or  six 
times  with  the  precipitant,  dried,  and  ignited.  After  all  of  the 
carbon  had  burned  off,  the  residue  was  fused  with  potassium 
bisulphate,  boiled  up  with  water,  filtered,  washed,  ignited  and  the 
columbic  oxide  weighed.  The  tungstic  oxide  was  obtained  by 
difference. 


No.  of  Cb205  W03  Cb205  W03 

sample.  taken.  taken.  found.  by  difference. 

1  .  0.2086  0.0986  0.2078  O.0994 

2  .  0.3218  0.1500  0.3208  0.1510 

3  .  0.5004  0.1000  0.4951  0.1053 

4  .  0.2026  O.IOOO  0.2032  0.0994 

5  .  0.1503  0.1200  0.1506  0.1197 


When  this  method  was  applied  to  a  solution  containing  un¬ 
known  quantities  of  columbic  and  tungstic  acids,  a  solution  of 
mercurous  nitrate  was  added,  and  then  a  slight  excess  of  nitric 
acid.  Freshly  precipitated  mercuric  oxide  was  then  added  and 
the  solution  was  boiled  five  minutes.  As  soon  as  the  precipitate 
had  settled,  it  was  filtered  out  and  washed  with  boiling  water.  It 
was  dried,  ignited,  and  the  columbic  and  tungstic  oxides  weighed 
together.  The  two  oxides  were  then  separated  by  the  method 
described  above.  Very  fair  results  were  obtained.  They  varied 
0.3-0.5  per  cent,  from  the  mean. 

CONCLUSIONS. 

From  a  study  of  the  results  obtained  it  can  be  seen  that  this 
method  gives  very  good  results.  Better  results  were  obtained 
from  this  method  than  from  a  sodium  carbonate  and  sulphur 
fusion.  It  can  be  carried  out  in  a  short  time  and  is  very  easy  to 
manipulate.  It  was  not  tried  on  a  mixture  of  a  trace  of  tungstic 
oxide  and  a  large  quantity  of  columbic  oxide  but  it  would  seem 
that  very  good  results  ought  to  be  obtained. 

This  method  was  not  applied  to  a  separation  of  tungstic  and 


tantalic  acids,  but,  from  the  results  with  columbium,  there  should 
be  no  difficulty  in  applying  it  to  a  separation  of  these  two  acids. 


acknowledgment. 

This  investigation  was  undertaken  at  the  suggestion  of  Prof. 
Edgar  F.  Smith,  and  I  take  this  opportunity  of  sincerely  thanking 
him  for  his  encouragement  and  ready  advice  throughout  the  work. 


